Partially crosslinked polymer for bilayer photoresist

ABSTRACT

The present invention provides photoresist monomers, photoresist polymers derived from the same, processes for producing such photoresist polymers, photoresist compositions comprising such polymers, and processes for producing a photoresist pattern using such photoresist compositions. In particular, photoresist monomers of the present invention comprise a moiety of Formula 4:                    
     where R 1 , R 2 , R 3  and R 4  are those defined herein. Photoresist polymers of the present invention have a relatively high etching resistance, and therefore are useful in a thin resist process and a bilayer photoresist process. Moreover, photoresist polymers of the present invention have a high contrast ratio between an exposed region and a non-exposed region.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to photoresist monomers suitable for abilayer photoresist, polymers derived therefrom and photoresistcompositions comprising such polymers. In particular, the presentinvention relates to photoresist monomers comprising a silicon moiety.

2. Description of the Background Art

Some semiconductor manufacturing processes use photoresist copolymersderived from a monomer comprising an alicyclic compound to formultrafine patterns. However, the yield of photoresist polymers fromthese compounds is relatively low resulting in increased manufacturingcosts. While the yield of acrylates polymerization is high, theresulting photoresist polymers have a weak etching resistance, therebylimiting its use.

Forming an ultrafine pattern below 0.13 m using a conventionalphotoresist coating thickness results in a high aspect ratio which maycause the pattern to collapse. And if the coating thickness is reduced,the resulting photoresist coating often has low or no etchingresistance. Thus, it is difficult to perform following, or successiveprocesses after etching process using conventional photoresist polymers.

One method for overcoming the above described limitations is to use a“thin resist-hard mask” process, which generally involves reducing acoating thickness of the photoresist composition and introducing a hardmask below the photoresist film coating. Another method is to use abilayer photoresist comprising silicon, which involves coating a bottomanti-reflective coating material (BARC), g-line photoresist or i-linephotoresist on the substrate and then coating a silicon comprisingphotoresist thereon. The resulting photoresist film is exposed, and theupper layer (i.e., photoresist comprising silicon) is wet developed toform an upper layer photoresist pattern. The lower layer is drydeveloped using O₂ plasma and the upper photoresist pattern as a mask toform a lower layer resist pattern. This process reduces or eliminatesthe occurrence of photoresist pattern collapse.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide aphotoresist monomers comprising silicon, photoresist polymers forbilayer resist derived from the same, and a process for preparing suchphotoresist polymers.

Another object of the present invention is to provide photoresistcompositions comprising such photoresist polymers.

Still another object of the present invention is to provide asemiconductor device produced by using such a photoresist composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a process for forming a photoresist pattern inaccordance with a preferred embodiment of the present invention; and

FIGS. 2 to 4 is a photograph showing patterns obtained in Examples 7 to9.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present invention provides a photoresist monomerselected from the group consisting of compounds of the formula:

where

each of X₁, X₂, Y₁ and Y₂ is independently alkylene, preferablymethylene or ethylene;

R₅ is hydrogen or alkyl, preferably hydrogen or methyl;

s and t are integers from 0 to 2;

n is an integer from 1 to 5; and

X is a moiety of the formula:

where

each of R₁, R₂, R₃ and R₄ is independently hydrogen, C₁-C₁₀ alkyl, orC₁-C₁₀ alkyl comprising an ether linkage.

In one particular embodiment of the present invention, the photoresistmonomers is selected from the group consisting of compounds of theformula:

The present invention also provides a photoresist polymer derived from amonomer comprising a first monomer selected from the group consisting ofthe compounds of Formulas 1 to 3, and mixtures thereof.

Photoresist polymers of the present invention include a monomercomprising a silicon rich moiety of Formula 4. Preferably, photoresistpolymers of the present invention comprise from about 7 to about 30 wt %of silicon. Without being bound by any theory, it is believed that anexcellent etching resistance to oxygen afforded by the presentphotoresist polymers is due to the presence of such a relatively highamount of silicon. This etching resistance to oxygen makes photoresistpolymers of the present invention useful in a bilayer photoresistprocess. The present inventors have found that even a thin coating ofphotoresist polymers of the present invention provides a successfulultrafine pattern formation.

The monomer used to produce photoresist polymers of the presentinvention can further comprise a second monomer of the formula:

where

V₁ and V₂ are independently alkylene, preferably methylene or ethylene;

R₆ is an acid labile protecting group; and

p is an integer from 0 to 2.

The acid labile protecting group may be selected from the groupconsisting of tert-butyl, tetrahydropyran-2-yl, 2-methyltetrahydropyran-2-yl, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl, 1-methoxypropyl, 1-methoxy-1-methylethyl,1-ethoxypropyl, 1-ethoxy-1-methylethyl, 1-methoxyethyl, 1-ethoxyethyl,tert-butoxyethyl, 1-isobutoxyethyl and 2-acetylmenth-1-yl.

The monomer used to produce photoresist polymers of the presentinvention can further comprise a third monomer of the formula:

wherein

W₁ and W₂ are independently alkylene, preferably methylene or ethylene;

R₇ is C₁-C₁₂ alkyl comprising an ether linkage or C₁-C₁₂ alkylcomprising a hydroxyl group; and

q is an integer from 0 to 2.

The monomer used to produce photoresist polymers of the presentinvention can further comprise a fourth monomer which can providecross-linkage within the photoresist polymer. Preferably, the fourthmonomer is a compound of the formula:

where

Y is C₁-C₁₂ alkylene, oxygen, or C₁-C₁₂ alkylene comprising an etherlinkage;

each of R₈ and R₉ is independently hydrogen or alkyl, preferablyhydrogen or methyl; and

each of R₁₀, R₁₁, R₁₂ and R₁₃ is independently H, C₁-C₁₂ alkyl, orC₁-C₁₂ alkyl comprising an ether linkage.

The diacrylate crosslinking compound of Formula 7 improves thepolymerization yield of the polymer. In addition, the hydrophobicproperty in a non-exposed region of the photoresist is significantlyincreased due to the crosslinking. As a result, the developing solutiondoes not remove any significant amount of the photoresist polymer in thenon-exposed region, but the photoresist polymer in the exposed region isefficiently removed by the developing solution. Therefore, the contrastratio between the exposed region and the non-exposed region ofphotoresist polymers of the present invention is significantlyincreased.

The monomer used to produce photoresist polymers of the presentinvention can further comprise maleic anhydride as a fifth monomer.Maleic anhydride also increases the polymerization yield of the polymer.

Furthermore, the monomer used to produce photoresist polymers of thepresent invention can further comprise a sixth monomer of the formula:

where

Z is alkylene or oxygen, preferably methylene, ethylene or oxygen.

Photoresist polymers of the present invention comprise a number ofrelatively sterically large substituent groups. Thus, it is preferableto add the compound of Formula 8 having a relatively small sterichindrance as a spacer monomer so as to adjust a molecular weight of theresulting photoresist polymer and to improve the polymerization yield.

In one particular embodiment, polymers of the present invention isselected from the group of consisting of polymers of the formula:

wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁, R₁₂, R₁₃, Y, and nare those defined above; and

a, b, c, d, e and f individually denote the mole ratio of each monomer,with proviso that d is not 0.

The terminal groups of polymers depicted in the present disclosuredepend on the polymerization initiator and/or the polymerizationterminator used. In addition, as used throughout this disclosure, itshould be appreciated that the order of monomeric units represented inpolymer formulas of the present disclosure does not necessarily indicatethe actual order of such monomeric units in the polymers. Monomericunits represented in polymer formulas are intended to simply indicatethe presence of such monomeric units in the polymer. Moreover, thevariables represent the total relative ratio of each unit. For example,the total amount “d” in Formulas 9-11 above can be inter dispersedthroughout the polymer (not necessarily in same concentrations) or allor majority of such polymeric unit can be concentrated in one particularlocation of the polymer.

Preferably the ratio of a:b:c:d:e:f is 0-20 mol %:0-50 mol %:0-50 mol%:0.1-30 mol %:0-10 mol %:0-50 mol %.

Preferably, photoresist polymers of the present invention comprise thefirst, second and third monomers defined above, e.g., a, b and d inphotoresist polymers of formula 9-11 are not zero.

Preferred polymers of the present invention include polymers of theformula:

Preferably, the molecular weight of photoresist polymers of the presentinvention is in the range of from about 3,000 to about 50,000, and morepreferably from about 3,000 to about 20,000.

Photoresist polymers of the present invention can be prepared using avariety of methods including a radical polymerization of monomers with aconventional radical polymerization initiator. An exemplary procedurefor preparing polymers of the present invention includes the steps of:

(a) admixing

(i) a monomer selected from the group consisting of compounds ofFormulas 1 to 3, and mixtures thereof,

(ii) another monomer selected from the group consisting of compounds ofFormulas 5 to 8, and mixtures thereof,

(iii) maleic anhydride, and

(iv) a polymerization initiator; and

(b) polymerizing said admixture under conditions sufficient to producesaid photoresist polymer, preferably in an inert atmosphere, e.g.,nitrogen, argon or helium.

The polymerization process can be a bulk polymerization or a solutionpolymerization using any inert solvent. If a solution polymerizationprocess is used, the polymerization solvent is preferably selected fromthe group consisting of tetrahydrofuran, dimethylformamide, chloroform,ethylacetate, acetone, ethylmethylketone, dimethylsulfoxide, dioxane,benzene, toluene, xylene, and mixtures thereof. In addition, when thepolymer is prepared in a solid state, the polymerization solvent isselected from the group consisting of diethyl ether, petroleum ether,n-hexane, cyclohexane, methanol, ethanol, propanol and isopropylalcohol, preferably diethyl ether, petroleum ether and n-hexane.

Exemplary polymerization initiator is selected from the group consistingof 2,2′-azobisisobutyronitrile (AIBN), benzoyl peroxide, acetylperoxide, lauryl peroxide, tert-butylperoxide and bisazide compounds.

Polymerization reaction is typically performed at a temperature range offrom about 50° C. to about 120° C., and preferably from about 50° C. toabout 80° C. With a typical reaction time of from about 4 to about 24hours.

The present invention also provides a photoresist composition comprising(i) a photoresist polymer described above, (ii) a photoacid generator,and (iii) an organic solvent.

Photoacid generators include onium type compounds, halogen compounds,diazoketone compounds, sulfone compounds and sulfonic acid compounds.More preferably, the onium type compounds containing sulfides and iodideare employed. In one particular embodiment of the present invention, thephotoacid generator is selected from the group consisting of diphenyliodide hexafluorophosphate, diphenyl iodide hexafluoroarsenate, diphenyliodide hexafluoroantimonate, diphenyl p-methoxyphenyl triflate, diphenylp-toluenyl triflate, diphenyl p-isobutylphenyl triflate, diphenylp-tert-butylphenyl triflate, triphenylsulfonium hexafluororphosphate,triphenylsulfonium hexafluoroarsenate, triphenylsulfoniumhexafluoroantimonate, triphenylsulfonium triflate,dibutylnaphthylsulfonium triflate, and mixtures thereof.

Typically, the amount of photoacid generator used is from about 0.05% byweight to about 10% by weight of the photoresist polymer. It has beenfound by the present inventors that when the amount of photoacidgenerator used is less than about 0.05%, the photosensitivity of thephotoresist composition is significantly decreased. And when the amountof photoacid generator used is greater than about 10%, a poor patternformation results, presumably due to its high absorption of deep ultraviolet light (DUV).

The organic solvent is preferably selected from the group consisting ofcyclohexanone, cyclopentanone, methyl 3-methoxypropionate, ethyl3-ethoxypriopionate, propyleneglycol methyletheracetate, and mixturesthereof. The amount of the organic solvent used is preferably in therange of from about 500% by weight to about 2000% by weight of thephotoresist polymer. When the amount of the solvent in the photoresistcomposition is about 1000% by weight of the polymer, a photoresist filmhaving thickness of 0.2 μm can be readily obtained.

Another aspect of the present invention provides a process for forming aphotoresist pattern using the photoresist composition described above.The process for forming a photoresist pattern includes the steps of:

(a) coating a photoresist composition described above on a substrate ofa semiconductor element to form a photoresist film;

(b) exposing the photoresist film to light using a light source; and

(c) developing the photoresist film to produce the photoresist pattern,

Photoresist compositions of the present invention can be used in asingle layer photoresist pattern formation process as described above.Alternatively, photoresist compositions of the present invention can beused in a bilayer photoresist pattern formation process, which generallyinvolves coating the semiconductor substrate with a bottomanti-reflective coating material (BARC), g-line photoresist or i-linephotoresist to produce a lower layer film, and coating the lower layerfilm with the photoresist composition described above to produce anupper layer photoresist film.

The photoresist pattern formation process can further include the stepsof heating (i.e., baking) the substrate before and/or after the step (b)described above. Moreover, in the bilayer photoresist pattern formationprocess, the baking step can be performed after forming the lower layerfilm.

In the single layer photoresist pattern formation process, the exposedphotoresist film can be developed by contacting it with an alkalinedeveloping solution under conditions sufficient to produce thephotoresist pattern. In the bilayer photoresist pattern formationprocess, the exposed photoresist film can be developed by contacting theupper layer photoresist film with an alkaline solution under conditionssufficient to produce an upper layer photoresist pattern, and contactingthe lower layer photoresist film with O₂ plasma using the upper layerphotoresist pattern as a mask under conditions sufficient to produce thephotoresist pattern. This bilayer photoresist pattern formation processis illustrated in FIG. 1, where the dry development is performed usingO₂ plasma.

As illustrated in FIG. 1, a lower layer material 13, such as a bottomanti-reflective coating material (BARC), g-line photoresist or i-linephotoresist, is coated on a wafer 11. Thereafter, the photoresistcomposition 15 of the present invention is coated on the lower layermaterial 13. The upper layer photoresist 15 is exposed to light using anexposure mask (A). Typically, the light source is ArF exposer (λ=193nm), KrF exposer (λ=248 nm), VUV exposer (λ=157 nm), EUV exposer (λ=13nm), E-beam or X-ray. The exposed upper layer photoresist film 15 isdeveloped using 0.1 to 10 wt % aqueous tetramethylammonium hydroxide(TMAH) solution (B) to produce an upper layer photoresist pattern. Usingthe upper layer photoresist pattern as a mask, the lower layer material13 is dry developed using O₂ plasma, thereby forming a lower layermaterial pattern. It is believed that during this O₂ plasma drydeveloping process, a silicon oxide film 17 is produced from the upperlayer photoresist pattern which comprises the photoresist compositioncomprising silicon. The exposed lower layer material 13 and the siliconoxide film 17 is removed to form a photoresist pattern (C and D).

As discussed above, photoresist compositions of the present inventioncomprise a photoresist polymer which is derived from a relativelysilicon rich photoresist monomer. Silicon present in photoresistcompositions of the present invention (7 to 30% by weight of thephotoresist polymer) forms a silicon dioxide film during a dry O₂ plasmaetching process, thus providing a superior etching resistance.Therefore, even if a relatively inexpensive g-line or i-linephotoresist, or general BARC is used as a lower layer film material, aphotoresist pattern can be successfully produced using a thin film ofphotoresist composition of the present invention. For example, aphotoresist film having a thickness of 2000 Å or less can be easilyetched without the problems associated with conventional photoresistcompositions. And since a thin photoresist film typically has a lowlight absorption, photoresist compositions of the present invention areuseful in photolithography processes that use an ultrashort wavelengthor an electron beam.

Yet another aspect of the present invention provides a semiconductorelement manufactured using a photoresist composition described above.

Additional objects, advantages, and novel features of this inventionwill become apparent to those skilled in the art upon examination of thefollowing examples thereof, which are not intended to be limiting.

EXAMPLES I. PREPARATION OF PHOTORESIST MONOMERS Example 1

Synthesis of ethylene glycol 2,4,6,8-tetramethylcyclotetrasiloxanylether acrylate

To a solution containing 1M of 2,4,6,8-tetramethylcyclotetrasiloxane and0.01 g of (CH₃CO₂)₂Zn was slowly added 1M of 2-hydroxyethyl acrylate.The resulting mixture was stirred for 12 hours at a room temperature.Thereafter, 200 mL of benzene and 200 mL of cold water were added. Theorganic layer was separated, washed with 200 mL of cold water, driedover MgSO₄, filtered and concentrated by distillation to provide thetitle compound of Formula 1A (yield: 97%).

Example 2

Synthesis of ethylene glycol 2,4,6,8-tetramethylcyclotetrasiloxanylether 5-norbornene-2-carboxylate

To a solution containing 1M of 2,4,6,8-tetramethylcyclotetrasiloxane and0.01 g of (CH₃CO₂)₂Zn was slowly added 1M of2-hydroxyethyl-5-norbornene-2-carboxylate. The resulting mixture wasstirred for 24 hours at a room temperature. Thereafter, 200 mL ofbenzene and 200 mL of cold water were added. The organic layer wasseparated, washed with 200 mL of cold water, dried over MgSO₄, filteredand concentrated by distillation to provide the title compound ofFormula 1A (yield: 97%).

Example 3

Synthesis of(5-norbornene-2-methoxy)2,4,6,8-tetramethylcyclotetrasiloxane

The procedure of Example 1 was repeated using 1M of5-norbornene-2-methanol instead of 1M of 2-hydroxyethyl acrylate toprovide the title compound of Formula 3A (yield: 98%).

II. PREPARATION OF PHOTORESIST POLYMERS Example 4

Synthesis of Poly{5-norbornene-2-(3-hydroxymethyl-3-ethyl)butylcarboxylate-3-carboxylic acid/tert-butyl5-norbornene-2-carboxylate/maleic anhydride/neopentylglycoldiacrylate/ethyleneglycol 2,4,6,8-tetramethylcyclotetrasiloxanyl etheracrylate}

To 200 mL of tetrahydrofuran was added 0.1 mole of5-norbornene-2-(3-hydroxymethyl-3-ethyl)butyl carboxylate-3-carboxylicacid, 0.4 mole of tert-butyl 5-norbornene-2-carboxylate, 0.5 mole ofmaleic anhydride, 0.01 mole of neopentylglycol diacrylate, 0.1 mole ofethyleneglycol 2,4,6,8-tetramethylcyclotetrasiloxanyl ether acrylate,and 3 g of AIBN. The mixture was heated to 65° C. for 8 hours.Thereafter, ether/diethyl ether (2:1) solution was added to the reactionmixture and the solid was filtered and dried to provide the titlepolymer of Formula 9A (yield: 62%).

Example 5

Synthesis of Poly{5-norbornene-2-(3-hydroxymethyl-3-ethyl)butylcarboxylate-3-carboxylic acid/tert-butyl5-norbornene-2-carboxylate/maleic anhydride/2,5-dimethyl-2,5-hexanedioldiacrylate/ethyleneglycol 2,4,6,8-tetramethylcyclotetrasiloxanyl5-norbornene-2-carboxylate}

The procedure of Example 4 was repeated using 0.1 mole of5-norbornene-2-(3-hydroxymethyl-3-ethyl)butyl carboxylate-3-carboxylicacid, 0.4 mole of tert-butyl 5-norbornene-2-carboxylate, 0.5 mole ofmaleic anhydride, 0.01 mole of 2,5-dimethyl-2,5-hexanediol diacrylate,0.1 mole of ethyleneglycol 2,4,6,8-tetramethylcyclotetrasiloxanyl5-norbornene-2-carboxylate and 3 g of AIBN to provide the title polymerof Formula 10A (yield 58%).

Example 6

Synthesis of Poly{5-norbornene-2-(3-hydroxymethyl-3-ethyl)butylcarboxylate-3-carboxylic acid/tert-butyl5-norbornene-2-carboxylate/maleic anhydride/2,5-dimethyl-2,5-hexanedioldiacrylate/(5-norbornene-2-methoxy)2,4,6,8-tetramethylcyclotetrasiloxane/norbornene}

The procedure of Example 4 was repeated using 0.1 mole of5-norbornene-2-(3-hydroxymethyl-3-ethyl)butyl carboxylate-3-carboxylicacid, 0.35 mole of tert-butyl 5-norbornene-2-carboxylate, 0.55 mole ofmaleic anhydride, 0.01 mole of 2,5-dimethyl-2,5-hexanediol diacrylate,0.1 mole of(5-norbornene-2-methoxy)2,4,6,8-tetramethylcyclotetrasiloxane, 0.03 moleof norbornene and 3 g of AIBN to provide the title polymer of Formula11A (yield: 61%).

III. PREPARATION OF PHOTORESIST COMPOSITION AND FORMATION OF PATTERNExample 7

A photoresist composition was prepared by adding 10 g of photoresistpolymer prepared in Example 4 and 0.12 g of triphenylsulfonium triflateto 150 g of ethyl 3-ethoxypropionate solvent, and filtering theresulting mixture through a 0.10 μm filter.

I-line photoresist was coated on a silicon wafer to form a lower layerwith a thickness of about 5000 Å. The coated silicon wafer was softbaked. Thereafter, 1 mL of the photoresist composition was spin coatedon to the silicon wafer and baked at 130° C. for 90 seconds. The bakedphotoresist film was exposed to light using an ArF exposer andpost-baked at 130° C. for 90 seconds [see FIG. 1(A)]. The exposedphotoresist film was developed using a 2.38 wt % aqueous TMAH solutionto produce an upper layer photoresist pattern [see FIG. 1(B)]. The lowerlayer photoresist was dry developed with O₂ plasma using the upper layerpattern as a mask to form a lower layer photoresist pattern. It wasobserved that during the O₂ plasma dry etching process a silicon oxidefilm was produced from the upper layer photoresist pattern containingsilicon. The exposed lower layer photoresist and the silicon oxide filmwere removed [see FIGS. 1(C) and 1(D), respectively] providing aphotoresist pattern of 0.12 μm L/S (see FIG. 2).

Example 8

The procedure of Example 7 was repeated using 10 g of photoresistpolymer prepared in Example 5 instead of photoresist polymer prepared inExample 4 to provide a photoresist pattern of 0.12 μm L/S (see FIG. 3).

Example 9

The procedure of Example 7 was repeated using 10 g of photoresistpolymer prepared in Example 6 instead of photoresist polymer prepared inExample 4 to provide a photoresist pattern of 0.13 μm L/S (see FIG. 4).

As discussed above, photoresist compositions of the present inventionare prepared using a silicon-rich photoresist monomer. The photoresistcomposition contains a proper amount of silicon, i.e., about 7 to about30% by weight of the photoresist polymer. When etched by oxygen, thephotoresist composition of the present invention forms a silicon oxidefilm resulting in a superior etching resistance relative to conventionalphotoresist compositions. Therefore, even if a relatively inexpensiveg-line or i-line photoresist, or general BARC is used as a lower layerfilm material, a photoresist pattern can be successfully produced usinga thin film of photoresist composition of the present invention, e.g.,thickness of 2000 Å or less. Moreover, a bilayer photoresist patternforming process can be used to produce a minute pattern without anysignificant pattern collapse resulting in a significant reduction in theproduction cost of semiconductor devices. Furthermore, a photoresistfilm having a thickness of 2000 Å or less can be easily etched withoutthe problems associated with conventional photoresist compositions. Andsince a thin photoresist film typically has a low light absorption,photoresist compositions of the present invention are useful inphotolithography processes that use an ultrashort wavelength or anelectron beam.

In some embodiment, photoresist polymers of the present inventioninclude diacrylate cross-linking monomers which increases thepolymerization yield. This cross-linking can also improve a contrastratio between the exposed region and the non-exposed region.

The foregoing discussion of the invention has been presented forpurposes of illustration and description. The foregoing is not intendedto limit the invention to the form or forms disclosed herein. Althoughthe description of the invention has included description of one or moreembodiments and certain variations and modifications, other variationsand modifications are within the scope of the invention, e.g., as may bewithin the skill and knowledge of those in the art, after understandingthe present disclosure. It is intended to obtain rights which includealternative embodiments to the extent permitted, including alternate,interchangeable and/or equivalent structures, functions, ranges or stepsto those claimed, whether or not such alternate, interchangeable and/orequivalent structures, functions, ranges or steps are disclosed herein,and without intending to publicly dedicate any patentable subjectmatter.

What is claimed is:
 1. A photoresist polymer derived from a monomercomprising a first monomer selected from the group consisting ofcompounds of the formula:

and mixtures thereof, wherein X₁, X₂, Y₁ and Y₂ are alkylene; R₅ ishydrogen or alkyl; s and t are integers from 0 to 2; n is an integerfrom 1 to 5; and X is a moiety of the formula:

wherein each of R₁, R₂, R₃ and R₄ is independently hydrogen, C₁-C₁₀alkyl, or C₁-C₁₀ alkyl comprising an ether linkage.
 2. The photoresistpolymer of claim 1, wherein each of X₁, X₂, Y₁ and Y₂ is independentlymethylene or ethylene.
 3. The photoresist polymer of claim 1, wherein R₅is hydrogen or methyl.
 4. The photoresist polymer of claim 1, whereinsaid first monomer is selected from the group consisting of compounds ofthe formula:


5. The photoresist polymer of claim 1, wherein the molecular weight ofsaid photoresist polymer is in the range of from about 3,000 to about50,000.
 6. The photoresist polymer according to claim 1, wherein saidmonomer further comprises a second monomer of the formula:

wherein V₁ and V₂ are alkylene; R₆ is an acid labile protecting group;and p is an integer from 0 to
 2. 7. The photoresist polymer of claim 6,wherein each of V₁ and V₂ is independently methylene or ethylene.
 8. Thephotoresist polymer of claim 6, wherein said acid labile protectinggroup is selected from the group consisting of tert-butyl,tetrahydropyran-2-yl, 2-methyl tetrahydropyran-2-yl,tetrahydrofuran-2-yl, 2-methyl tetrahydrofuran-2-yl, 1-methoxypropyl,1-methoxy-1-methylethyl, 1-ethoxypropyl, 1-ethoxy-1-methylethyl,1-methoxyethyl, 1-ethoxyethyl, tert-butoxyethyl, 1-isobutoxyethyl and2-acetylmenth-1-yl.
 9. The photoresist polymer according to claim 6,wherein said monomer further comprises a third monomer of the formula:

wherein W₁ and W₂ are alkylene; R₇ is C₁-C₁₂ alkyl comprising an etherlinkage or C₁-C₁₂ alkyl comprising a hydroxyl group; and q is an integerfrom 0 to
 2. 10. The photoresist polymer of claim 9; wherein each of W₁and W₂ is independently methylene or ethylene.
 11. The photoresistpolymer according to claim 9, wherein said monomer further comprises across-linking monomer of the formula:

wherein Y is C₁-C₁₂ alkylene, oxygen, or C₁-C₁₂ alkylene comprising anether linkage; each of R₈ and R₉ is independently hydrogen or alkyl; andeach of R₁₀, R₁₁, R₁₂ and R₁₃ is independently hydrogen, C₁-C₁₂ alkyl,or C₁-C₁₂ alkyl comprising an ether linkage.
 12. The photoresist polymerof claim 11, wherein each of R₈ and R₉ is independently hydrogen ormethyl.
 13. The photoresist polymer of claim 11, wherein said monomerfurther comprises maleic anhydride.
 14. The photoresist polymer of claim13, wherein said monomer further comprises a sixth monomer of theformula:

wherein Z is alkylene or oxygen.
 15. The photoresist polymer of claim14, wherein Z is methylene, ethylene or oxygen.
 16. The photoresistpolymer of claim 15, wherein said photoresist polymer is selected fromthe group consisting of polymers of the formula:

wherein R₁, R₂, R₃, R₄, R₅, and n are those defined in claim 5; R₆ isthat defined in claim 9; R₇ is that defined in claim 12; R₈, R₉, R₁₀,R₁₁, R₁₂, R₁₃, and Y are those defined in claim 14; and a, b, c, d, eand f individually denote a mole ratio of each monomer, provided theratio of a:b:c:d:e:f is 0-20 mol %:0-50 mol %:0-50 mol %:0.1-30 mol%:0-10 mol %:0-50 mol %.
 17. The photoresist polymer of claim 16,wherein each of R₅, R₈ and R₉ is independently hydrogen or methyl. 18.The photoresist polymer of claim 16, wherein said photoresist polymer isselected from the group consisting of compounds of the formula:


19. A photoresist composition comprising: (i) photoresist polymerderived from a monomer comprising a first monomer selected from thegroup consisting of compounds of the formula:

and mixtures thereof, wherein X₁, X₂, Y₁ and Y₂ are alkylene; R₅ ishydrogen or alkyl; s and t are integers from 0 to 2; n is an integerfrom 1 to 5; and X is a moiety of the formula:

wherein each of R₁, R₂, R₃ and R₄ is independently hydrogen, C₁-C₁₀alkyl, or C₁-C₁₀ alkyl comprising an ether linkage; (ii) a photoacidgenerator; and (iii) an organic solvent.
 20. The photoresist compositionof claim 19, wherein said photoacid generator is selected from the groupconsisting of diphenyl iodide hexafluorophosphate, diphenyl iodidehexafluoroarsenate, diphenyl iodide hexafluoroantimonate, diphenylp-methoxyphenyl triflate, diphenyl p-toluenyl triflate, diphenylp-isobutylphenyl triflate, diphenyl p-tert-butylphenyl triflate,triphenylsulfonium hexafluororphosphate, triphenylsulfoniumhexafluoroarsenate, triphenylsulfonium hexafluoroantimonate,triphenylsulfonium triflate, dibutylnaphthylsulfonium triflate, andmixtures thereof.
 21. The photoresist composition of claim 19, whereinthe amount of said photoacid generator is in the range from about 0.05to about 10% by weight of said photoresist polymer.
 22. The photoresistcomposition of claim 19, wherein said organic solvent is selected fromthe group consisting of cyclohexanone, cyclopentanone, methyl3-methoxypropionate, ethyl 3-ethoxypriopionate, propyleneglycolmethyletheracetate, and mixtures thereof.
 23. The photoresistcomposition of claim 19, wherein the amount of said organic solvent isin the range of from about 500 to about 2000% by weight of saidphotoresist polymer.